Only Natural continued
by Outasync
Summary: My extension of a story started by StillThunder86. See A/N. How can they be there for each other when they're separated and held prisoner? Rated T for violence.
1. Chapter 1

_**A/N: This chapter is re-posted, with permission, from StillThunder86's original story ([FF] .net/s/6594349/1/Only_Natural) . It is included here only in order to have this story all in one place. So, as well as making it clear that I don't own TMNT, I should also point out that I don't own this chapter. Everything from chapter two onwards, however, is my own work - although StillThunder86 was kind enough to stick around and act as my beta. **_

_**If you like this chapter, go on over to her profile and check out some of her other stories: [FF] .net/u/2596218/**_

**CHAPTER ONE**  
><strong>Only Natural<strong>

"Are we supposed ta be seein' somethin' here?"

The strap binding Donatello's head made it impossible to look towards his brother. The best he could manage was a blurred, dark green figure at the edge of his vision. Just enough to see his brother was in the same position as himself.

Upright on a steel table, head strapped as back as neck and shell would allow. Three thick bands running across the chest, stomach, and thighs. Wrists and ankles shackled tight by leather cuffs.

They faced a shaded window viewing a small, white room. In the thirty minutes in which they'd demanded to know if the other was hurt, then established that neither was _lying_ about not being hurt, and tested the strength of their tethers, it remained empty.

But it made him nervous. Gave him that tingly being-watched sensation at the back of his neck.

"Don?"

"I'm not sure," he said at last. "But this is a two-way mirror."

"Like in interrogation rooms?"

"Yes."

Raphael went silent for a moment and when he spoke again, Donnie was startled at the tightness in his voice. "Who'd we have ta watch bein'…"

"Two guesses, Raph."

Only two others worth the ambush Bishop had set for them.

His remaining brother growled and Donnie heard him thrash. He bit his lip to keep from scolding him. They had to conserve their energy for whatever was coming. But Raph gave up after a minute and he was thankful he'd kept his mouth shut. He wasn't in the mood to be accused of being a Leo-substitute just then.

After that, they sat in silence and waited for their host to show up.

Silent, but not idle. Donatello wriggled and pulled at his own straps, sure that if he could just get a look at them, he'd see a way out. His wrists had been fixed into braces, leaving his fingers free, but keeping his joints immobile. Between that and the ache in his strained neck, he felt the first tendrils of claustrophobia tightening around his chest.

He took a few breaths and focused on the room in front of them. His brothers need him losing his head as much as they needed Raph exhausted. He had to calm down. He had to –

"Raph!"

"Wha'?" his brother snarled.

In the silent white, a tall panel had been withdrawn, creating a black void. A familiar, three-fingered hand curled out of the darkness and Leonardo slunk into sight.

"LEO!" Donnie flinched, his ears ringing. "Leo, we're here! Jes through da window! In here!"

Their brother turned in a slow circle, crouched low to brace himself on his fingertips. He had been stripped of his gear. When the panel slid back into place, he started, lunging for the corner and looking around with sharp, bird-like twitches.

"Leo!"

Don ground his teeth. "He can't hear you."

"No kiddin'," Raph growled. "Don't mean it can't make me feel betta…" His voice softened. "Why's he actin' like that?"

Leo rocked, gently, his arm wrapping around his knee as he started at the lights. His brow was mild and smooth and Donnie marveled at how young he seemed. "He's drugged."

Suddenly another panel, opposite their brother, rose. Thirty seconds later, a gearless Mikey was shoved inside. He spun, his lip drawn back and rushed at the hole even as it slammed back into place. Mikey sniffed at the blank surface, completely oblivious to his brother.

Who was staring at his back.

Ice flowed through the inventor's stomach.

Mikey worked his way left, his hands trailing over the wall. When he came to the window, he spread his fingers flat and exhaled a soft circle of moisture. Donnie strained forward, trying to examine his brother as the youngest tapped the glass, curiously.

"No..."

"Wha'?" Raph asked faintly.

"Look at his eyes."

Where should have been clear cerulean was a glinting shield of black.

Raph swore. "What is dat?"

"I have no idea."

Mikey's eyes trailed down a fixed on a spot near his elbow. His joyful face ignited with fury and he spun on his heel, tensing. Leo rose, snarling. His hands balled into fists. The youngest went forward, stretching to his toes to match his brother's height.

"Wh-what're dey -?"

Donatello's heart wrenched as he realized just what he was seeing. Mikey's blatant adoration of his oldest brother was gone. So was the subtle affection which always lined the leader's face. Leo's eyes sparked, dangerously, as he spread his shoulders and made a false charge, dropping Mike back a step. Leo eased away, the glass silencing the rough hiss he gave as he jerked his chin upward.

Don's tongue felt thick against the roof of his mouth. "They're challenging one another."

"For what?"

"I…I think it's territorial."

"WHAT?"

Leo bared his teeth and moved right, forcing Mikey to mirror the action. They crouched low, backs to the wall.

Raph's voice was low and tight again. "I didn' even know we were territorial."

A bitter smile touched the genius's mouth. "Who all is allowed near your room again?" Silence. They watched the circling continue, nauseous. "This is instinctual. They're mature males forced together in a small enclosure. It's only natural they'd have to establish a hierarchy between…"

"There ain't nothing _natural_ 'bout our brothas havin' a pisser over that POS room!" Raph roared. Then, he panted, "Leo'll kill 'im, won't he?"

Donnie flinched at the defeat in his brother's voice. He wished he could reach out to him, to even _look_ at him. To look at anything but the spectacle before him. "Not necessarily."

"Howya figure?"

He hesitated. They all knew he could not shut down the analytical side of his mind, but never before had he spoken his observations about any of _them_. It felt almost like a betrayal.

"Leo is most dangerous when he can detach, go cold. He sees fighting as an art and feels nothing when he loses himself in it. It becomes a task. A glorified kata he's already mastered. When he's not watching out for us, he's deadly. But Mikey treats a fight like a game he already knows he's winning. He runs on passion, making decisions on whatever feels right in the moment." He paused. "Passion is a lot closer to instinct than logic."

"So," came a deeper voice from behind, making them both jump. John Bishop emerged from Donnie's right, gliding to the window. "Who would you put your money on?"

"Bishop!" Raph hissed as horrified guilt tore Donatello's gut. He bit his lip, furiously. Of course Bishop had been with them this whole time! And he'd just given the man information on his brothers!

Stupid, stupid, stupid…

The agent's lenses flashed as he glanced back to them. "Good evening, gentlemen."

"Bishop, what is dis?" Raph snapped. "What did ya do to 'em?"

The man's eyes crinkled, merrily, as he returned his attention to the window, where the two mutants were still threatening. "My scientists have developed a serum I found quite intriguing. It lowers activity in the brain's frontal lobe, suppressing societal and habitual implications."

"Wanna try it in English, jerk?"

Donnie sighed, heavily. "Raph, the frontal lobe is where most of the personality is. Their reasoning, memories, inhibitions…"

"All temporarily repressed," Bishop grinned. "Isn't it astounding what science can do?"

A surge of heat stirred through Donnie. "This has nothing to do with - NO!"

His voice shattered as Leo leapt across the small space, a wild swing blazing over Mikey's head. He threw out his leg, catching the younger in the rump and sending him over the floor. Leo kicked off the wall and tackled the fallen warrior, grappling with him as they rolled. Mike twisted, violently, and sank his teeth into his leader's forearm. Leo's mouth went wide in a howl of pain and indignation as he ripped free.

Red dripped over white tiles. The leader stared, stunned, at the injury and slowly raised hate-filled eyes. Mikey's sneer was marred by his brother's blood. He charged now, his shoulder catching Leo in the gut and slamming him into the corner.

"Interesting," Bishop murmured.

Tears stung. It was far from interesting. It was grotesque and pitiful and Donnie prayed it wasn't being recorded. Leo would die of shame if he ever saw himself kneeing Mikey's side with a savage, half-cocked grin. Or discovering he'd thrown all his strength into a punch to his little brother's temple. "This is sick."

"We call it the 'Berserker,'" Bishop said, casually. Ignoring him. "Fitting, isn't it? The original test subjects tore each other apart. We've made adjustments as we could. But how much can you truly glean from rats?"

A gash lanced over Mikey's cheek.

A fierce uppercut pierced Leo's teeth into his tongue and blood flowed.

"I'm hoping your brothers can supply adequate results to enhance the serum. We just can't seem to find that pesky line between increased aggression and insanity." The agent tapped his chin, enthralled. "Just fascinating, isn't it? We all know Leonardo suffers from an alpha male complex. But to see it in Michelangelo as well…Interesting."

"Stop that!" Raph bellowed.

More droplets littered the tiles.

"Okay," Donnie breathed, angrily. "What do you want, Bishop? What do you want from us to stop this?"

Bishop hummed in his throat as Leo smacked headfirst into the glass and staggered back, dazed. Harder to see the difference in his dark eyes, but Donnie found the lack of intelligence in his leader's face to be just as chilling.

And heartbreaking. His shoulders heaved and his lips were drawn back, not to intimidate now, but to gulp air.

"Come on, Leo. Fight it!" Raph whispered. "Yerbetta than this, bro! Just stop…"

Black fire erupted and the glass wavered as the eldest's fists slammed it in frustration. He spun back to an expectant and equally exhausted opponent. They tore at one another as they went down. Mikey's arm snaked out and he jammed his elbow back short and quick. Leo fell back, clutching an unnatural bulge from his shoulder. His heel caught Mike in the chin, snapping his neck back.

"Bishop, please!" Donnie wailed. "They're killing each other!" Leo backhanded the other with his good arm. "Look, you can have me instead! Whatever tests or samples you need, all right? Just stop this!"

The man stuck out his lower lip, as if considering. "No."

"No?"

"Honestly, Donatello, I'm not interested." He turned his back on the room, gliding before the turtle. "No offense, but I've lost enough equipment and expense on you. Besides, your DNA could still be corrupted from our last encounter. Any tests run would not be reliable. I don't need you…"

"Whaddabou' me?"

Raph's words, even whispered, felt like a slap . "No!"

"Shut-it, Braniac."

Bishop's eyes slid to his right and he eased just out of Donatello's sight. He jerked at his shackles, fighting his own growing scream of frustration. He wasn't accustomed to feeling helpless.

He heard the low taunt in Raph's voice and his brother's arrogant smile flickered behind Don's eyes. "C'mon, B. I'm healthy as a horse and free of your alien-goo. Tried smokin' once, didn' like it. Had a beer here and there, but how crucial is one turtle's liver to yer ol' serum?"

"Minimal."

"There you go. Just get them outta there an' I won't make a fuss 'bout anythin'. Deal?"

"Raph, you can't…" Donnie's voice broke.

"You were jes' offerin', little bro."

"That's different!"

"Is it?" Bishop passed by with a smirk. He pressed his earpiece. "Send in Stone and Phelps. Cut the test, we have enough." He resumed his place at the window as Leo struggled to break free of a chokehold. Dark triumph flickered over the youngest's face. "Cut it now."

The lights went wild, flashing in and out. Donnie heard the faintest, muffled screech of an alarm.

Leo and Mikey fell away from each other, hands clamping over their heads. In the strobe lighting, he spotted a man lean through one of the panels to aim a tranquilizer gun. He ground his teeth as Mikey's bleeding frame went down. Leo crashed a second later and the siren died. Light flooded the room again as scientists rushed for the mutants.

A door crashed open behind them, followed by the heavy-soled clunk of boots. Two men wheeled Raph forward and around Donnie. And as he went by, the older turtle mouthed: _Do something!_

Donnie watched him go, bewildered. Do? What _could_ he do?

Bishop waited until the door slammed before reaching for his earpiece again. "Take the initial stats on Leonardo and then keep him sedated. I don't want him trying anything clever. And don't underestimate Michelangelo, he's the tricky one. Secure him and monitor any residual side-effects." He paused. "And double the guard in Lab 5, we're going to have trouble in there," he looked at Donatello with a slight smile, "Promise or no promise."

He fell silent and his hands returned to his back. He continued to watch the swarming technicians. Donnie strained against at his restraints and attempted murder via glare. Both had failed results.

"Your eagerness to sacrifice yourself for the sake of your motley little family will never disappoint, will it? All four of you. Off goes your heroic sibling there, giving everything just to stop a silly little fight. Why? After all, he could be the next visitor to that room. I could break him in ways he can't fathom. Yet, there he goes. And I'll bet you'd be more than willing to take his place, knowing that." He snorted. "Rather self-destructive behaviour, isn't it?"

"But it's our way," Donnie whispered. "Better myself than one of my brothers. It's a concept understood and just as natural as breathing." He lifted shadowed eyes. "You'd know what it's like if you really had something to fight for."

The man lifted a brow, smirking. "The rat let you watch after-school specials, didn't he?" He shook his head and turned to leave. "Don't worry, Donatello, you'll get your chance to play the hero. I've other projects which don't involve DNA at all. You certainly won't feel left out." The door clicked quietly behind them.

Donatello went a little crazy then, kicking and arching as best he could, but the straps wouldn't give. He swore, bitterly, and fell against the table, panting. He needed a plan. He needed Leo to give him a plan to execute. That was what Donnie did, figured out the _how_ to Leo's strategizing.

The scientists succeeded in hauling the leader onto a stretcher. Leo's arm flopped, placidly, over the edge and Donnie stared at it, hating his own helplessness.


	2. Chapter 2

_**A/N: This is where I take StillThunder86's idea and run with it to tell my own story. I couldn't have done it without her. Check out her profile: [FF] .net/u/2596218/**_

**CHAPTER TWO**  
><strong>Mack<strong>

Raphael felt sick as he was wheeled from the room, leaving Donatello alone and having no option but to trust that Bishop would keep his word. He was pushed through a door with the number '5' painted large on it. He felt shadow fall over him as someone stepped up behind him, a sharp pain in his arm, and then he was being tipped forward. Suddenly, his bonds were released and he fell off the table to land on the concrete floor. His quick reflexes meant that he landed on his feet, but when he tried to grasp his weapons and spin to face his captors he realised two things. First, his sais were missing, and second, his legs didn't seem to be working properly. Cramp, from being strapped on that table? Ah, no. He only just had time to recognise that he'd been drugged before sleep overtook him. His last thought as he hit the floor was for his brothers.

-TMNT-

He woke up to find himself stripped of his belt and mask, but otherwise unharmed. He was slightly surprised, as he had expected to come to on one of Bishop's examination tables – or not at all. One wall of his cell turned out to be made of bars, covered in sharp barbs. He hadn't noticed that when he came in. Then again, he hadn't noticed much about where he was taken. He was more concerned about where his brothers were. He stiffened as he saw Bishop on the other side of those bars. The man was smiling his usual, superior smirk, the one that made Raph want to break his face every time he saw it.

"Good, you're awake," Bishop observed. He made a note on his clipboard, studying the turtle as if he were a particularly interesting specimen in a jar. Raph felt his temper start to boil, but he knew that trying to grab at the man through the bars wouldn't do any good. Bishop had already shown himself to be too fast to be caught so easily, and Raph would only injure himself on the sharp barbs that lined the bars of his cell. He forced himself to stay still as he met Bishop's gaze, stare for stare.

"What have you done with 'em?" he demanded. "Leo, and Mikey and Don – where are they?"

"They are safe – for now. Look." Bishop took a remote control from his pocket and pointed it at a monitor in the corner of the room behind him. Through the bars of his cell, Raph could see his brothers on the screen. They were all together, in the room where he had left Don. Don was free from the table he had been strapped to, and was busy tending to Leo's injuries. Raph could see that Mikey was already lying on another table, a bandage around his head.

"Your brothers have food, water and all the medical supplies they need. They are being treated well. If you want this situation to continue, you will co-operate with me in everything. Do you understand?"

Raphael glared at him. When he didn't answer, Bishop pressed another button on his remote. In the room holding his brothers, the wildly flashing lights started up again. Although he couldn't hear anything from the monitor, it was clear from the way they held their ears that there must be a horrible noise going to match the strobe lighting. In fact, he thought he could hear it, echoing far away down a distant corridor. He glared at Bishop, who merely raised an eyebrow at him.

"I said, do you understand?" he repeated, without emphasis. He didn't look at the screen, preferring to watch Raphael's horrified reaction instead.

"Yes! Yes, I understand!" the distressed turtle snapped. "Cut it out! Right now!"

Bishop pressed another button, but the lights didn't stop flashing. Rather, they got faster, and brighter. The sound was louder, too. Raphael could hear it clearly, now. He made a lunge for the remote, not caring that he would rip his arm on the barbs. But as his hand approached the bars, a shock of electricity arced from them to his arm. The surprise, as much as the pain, threw him back against the far wall of his cell.

"I give the orders here, not you. Is that clear?" Bishop's voice stayed calm, but the menace in his eyes was chilling.

"Yeah, OK. Just stop hurting them. Please." he added, in response to Bishop's raised eyebrow.

"That's better," said the scientist, approvingly, as he once more lifted the remote. Raph had just enough time to see the lights return to normal, and register the sound shutting off, before the screen went blank. "As long as you behave, they will not be harmed. Resist me, and... well, I'm sure you know that I have far worse things than light and sound at my disposal. Consider this your first, and last, warning."

Raphael slumped against the wall of his cell, staring at the blank screen that had shown him his brothers.

"Hang in there, guys," he said. "I won't let him hurt you again. I promise."

-TMNT-

Donatello's face creased into a worried frown as he looked over his brothers' injuries. He had done all he could to clean and treat their wounds, now it was a question of waiting for them to wake up. He wouldn't know what sort of lasting effect Bishop's serum had had on them until then. And when they did wake, he didn't know what to hope for. If they remembered nothing of the whole incident, then he would have to tell them what had happened, which he could hardly bear to think about. On the other hand, if he did have to tell them, at least he could give them the edited version. They would never have to know about the awful way they had looked at each other, dealing out vicious attacks and showing no restraint. But if they remembered everything... Don shook his head again, trying to dislodge the vision of Leo and Mikey unable to look at each other for guilt. He knew that he would be able to tell, as soon as they opened their eyes and saw one another. He would know at once whether or not they remembered. His mind played out both possible scenarios, and he honestly didn't know which one he dreaded more. The third possibility – that the serum had permanently damaged their minds – he refused to even consider.

Seeking something to keep his mind off his brothers' possible fates, Donatello obsessively checked and re-checked their medical supplies. Bishop had been thorough, giving him everything he needed to tend his brothers' injuries. Donatello could almost have been grateful for this, if it weren't Bishop fault that they were injured in the first place. There were a dozen clean dressings, of all sizes, along with enough bandages to wrap them both from head to foot many times over. Three bottles of antiseptic, and sterile needles and thread for stitches. Even warm and cold compresses, to reduce the pain and swelling of the bruises, and ease over-used muscles. They had everything they needed – except a way out of this place. Don stared at the table of supplies. Surely he could come up with _something_ from all this? He was the inventor, wasn't he? The clever one. They were depending on him.

Don could feel the panic rising in his chest again, and looked for another way to keep busy. As he re-checked Leo's bandages, the lights in the room suddenly began to flash furiously. A piercing wail seemed to be coming out of the walls, echoing around the small room. The dressing dropped from Don's nerveless hands as he screwed up his eyes and clutched at his head in an effort to block out the terrible noise. He squinted furiously against the lights to check on his brothers, and saw them both curled up on their tables, hands pressed to their ears and eyes tight shut. Michelangelo was shaking, and Leo's hands were clenched so tightly that the wound on his arm had re-opened. Donatello tried to reach for the bandage, but as soon as his hands left his ears the noise threatened to split his head. He fell to his knees as the noise intensified and the lights flashed faster and brighter. His only ray of hope was that all this noise was an alarm of some kind, and that it meant Raphael had escaped. If he could make himself work through it, maybe he could use the diversion of Raph's breakout to get his wounded brothers to safety.

Donatello stood, forcing his hands to his sides and his eyelids open. He reached again for Leo's arm, and the room went suddenly quiet. The lights stopped flashing and settled back to a soft, steady glow. A rush of relief was followed by a wave of concern for his brother. Did this mean he had been caught? Donatello felt suddenly guilty. What if Raph really had been causing a diversion, trusting him to do something with this chance, and he'd wasted it? Raph was relying on him – they all were. He was letting them down. Donatello sank to the floor, guilt crushing him so badly he could barely breathe.

He looked at Leo and saw blood seeping through the bandages on his arm. Donatello pulled himself together. This, at least, he could do. He went over to his older brother and began to change the dressing. He saw that both Leo and Mikey had their eyes open, although neither seemed truly aware of their surroundings. Don should have been relieved to see that the blackness was gone from their eyes, but the blankness that he saw there instead was almost worse. As he began to work on Leonardo's arm, the older turtle turned those blank eyes on him without recognition.

"Leo? It's going to be OK. I just need to get to your arm for a minute. OK, Leo?" Donatello kept his voice calm, but his heart was racing. He fought back tears as he focused on wrapping the clean dressing around his brother's arm. He didn't want to think about what would happen if Leo or Mikey were permanently damaged by this serum of Bishop's. He had never felt so alone, or so helpless.

"Don?" Leo sounded uncertain, as if he barely recognised the turtle standing at his side. "Don? Is that you? Where are we?"

"Leo? You're..." Don paused. He had been about to ask if his brother was alright, but, of course, he wasn't. "You're... awake," he substituted, feeling foolish. He glanced over at Mikey, who was trying to sit up.

"Hey, Donnie." Mikey said, blearily. "Whatcha doin'?"

Relief poured through Donatello, as he let the tears fall at last.

-TMNT-

Back in Raphael's cell, another wall rose to reveal another set of bars. These were smooth, but there were two sets, spaced four feet apart. On the far side of both sets of bars, Raph could see a figure curled on the floor, seemingly asleep. Bishop re-appeared behind the barbed wall.

"This is your first test," he announced, without preamble. "Mack here is another specimen of mine. You might be interested to know that the serum my team is currently developing was inspired by Mack. It used to be intelligent, once. Could talk as clearly as you or I. Well, as clearly as you, anyway. Somewhere along the line, though, Mack went feral. Any human intelligence it used to have appears to have been lost, subsumed by its animal nature. The serum currently under development aims to reproduce that response in a controlled manner. Meanwhile, Mack remains a useful benchmark."

Raph rolled his eyes at Bishop, and the creature in the far cell. "You say that like you expect me to care, Bishop," he said. "What's any of this got to do with me?"

"Rather a lot, I think you'll find. At the moment, Mack represents the raw, brutal nature of the Berserker without having to use the serum itself. You, meanwhile, are currently unaffected by any drug – beyond the residual effects of the tranquiliser from earlier. Observing your fighting styles will provide us with valuable information on the strengths and weaknesses of the Berserker method. Between you and Mack, we should be able to refine the serum to combine the best of both techniques."

The bars dividing his cell from Mack's started to move, one set moving up into the ceiling, the other sinking down into the floor. The creature in the corner stirred, as if familiar with the sound. Bishop brought his remote control from his pocket, and pointed it at the wall behind Mack. A light flashed, and the creature started.

"The fight will end when one of you is rendered helpless. You may defeat your opponent in any way you choose, but it's only fair to warn you that Mack will be trying to kill you. You may begin when ready." Bishop calmly replaced the remote control in his pocket, and readied his clipboard. Raph found his detached interest truly disgusting. He turned to where Mack was pacing on the far side of their battleground. The creature was watching him warily, as if trying to size up the threat he posed. Raphael adopted his fighting stance, wishing more than ever that he had his sais.

The creature growled low, baring its teeth at the turtle. In one bound, Mack cleared half the distance between them. Raphael barely had time to brace himself before the creature sprang again, aiming for the throat.

The fight was on.


	3. Chapter 3

_**A/N: Thanks to StillThunder86 for being a brilliant beta.**_

**CHAPTER THREE**  
><strong>Control<strong>

Leonardo blinked in the white room. The light seemed gentle now, but surely it had been hurting his eyes only a minute ago? Had he been ill, he wondered. He felt as though he had. He head was pounding, his arm hurt and he felt as though his insides had been stirred up with a spoon.

He looked across to where he thought he'd seen Michelangelo earlier. He had a mental image of Mikey attacking him, but dismissed it as a fever dream. There's no way his gentle, fun-loving brother could really be the black-eyed monster from his nightmare. In the dream, he'd fought back savagely. There'd been none of his normal control, no ninjitsu finesse, just raw brutality. He frowned, and wondered how sick he'd been to have crazy dreams like that. It was a bit disturbing how vivid they'd seemed at the time, and how clearly he remembered them now. But there was Mikey, same as ever, sitting on the edge of a table and pestering Don about something. Mikey turned and smiled, a little tightly, when he saw Leo was awake. Leonardo's eyes opened wide in horror – there was a soft dressing over his little brother's temple, held in place with a bandage around his head. Leo remembered landing a blow on the Mikey in his dream, in exactly the same place. He felt sick. Had he, in his fever, acted out his dream and _really_ attacked his youngest brother?

Donatello saw the look on Leonardo's face, and knew that he must have remembered something from the fight. He hurried over to reassure him.

"It's OK, Leo, it's over. It was Bishop, he drugged you both to make you fight. It's not your fault. None of it is your fault, Leo. You have to believe that." Don spoke with as much authority as he could muster, no easy task for the turtle who had always preferred to take the back seat in family arguments. He wasn't used to making people listen to him, in fact, quite the reverse. But it was vital that he get through to their leader at once. Raph was in who knew what sort of danger, and they didn't have time for Leo to go on a guilt trip.

"We need you, Leo," Don said, emphasising the 'need' strongly. "It's Bishop. He's got Raph."

"He's got all of us, bro," Mikey pointed out, his blue eyes clouding dark for a moment and an uncharacteristic bitterness tingeing his voice. "That was a sweet ambush he set up."

"So glad you approve," said Bishop. He appeared at a window in their door, speaking to them through a microphone. "I admit, I was rather proud of it myself. So satisfying when everything goes to plan, don't you agree, Leonardo? You're the planner of this little team, aren't you? Well, don't make any plans for escaping. As your brother has told you, Raphael is helping me with my experiments. If you give me any trouble, _he_ will pay for it."

"Where's Raph?" Leo demanded, furiously. "What have you done with him?"

"I should point out that 'trouble' includes bad manners, Leonardo," Bishop observed. "I'll overlook it, this time, but be warned. Your brother is alive and well. Would you like to see him?"

"Well, duh!" Mikey snapped. "Where is he?" When Bishop didn't respond, Don said, more quietly,

"We would like to see our brother, yes." This only earned him a contemptuous smile.

"Ah? Manners?" Bishop prompted.

Leo bit down hard on the angry retorts that were springing to his lips. This man held all the cards right now, and there was nothing to be gained by antagonising him. With a quiet dignity, Leonardo stood tall in front of the window and looked Bishop in the eye.

"Would you please be so good as to let us see Raphael?" he asked, his voice nearly as calm as Bishop's own; his face as expressionless.

"Better," the scientist acknowledged. "Very well." And with his remote control, he activated a panel in the wall which slid back to reveal monitor.

"Your brother is sleeping, now. However, this was recorded only an hour ago. As you can see, he's doing quite well."

The three turtles watched in horrified fascination as some kind of wild animal lunged for their brother's throat.

-TMNT-

Raphael ducked at the last moment, bringing his forearm up in a horizontal block that hit the attacking creature in the throat. Mack's own momentum added to the force of the blow, and Raph heard the wind being knocked from his opponent's lungs. He stepped back, assessing the situation. He figured that having been winded, Mack would need a minute to recover, and Raph could use that time to his advantage. However, as soon as the animal's feet hit the ground, it sprang back up, ready to attack again.

Mack stayed low this time, focusing on Raphael's legs and feet; trying to find a good target while avoiding a kick. Raphael wished, yet again, for his sais. With Mack's pounce-attack style, it would be simple enough to hold him off, letting his opponent wear himself out while Raphael conserved his energy. However, without weapons, he couldn't be so confident of blocking all Mack's attacks. He would have to go on the offensive, and try to get the creature to back down.

Mack was the size of a large dog, and probably weighed about the same as Raphael himself. However, Mack had all his power in his hindquarters and attacked forward, while the ninja turtle could use his height to attack downwards. Raph allowed himself a small smile. It wasn't often he had the height advantage in a fight. He circled around his foe, trying to get behind or beside him. If he could wrestle the animal from behind, it would be harder for Mack to use his teeth or claws. Raph timed his move carefully, and struck, wrapping strong arms around Mack's throat, chest and forelegs and pinning him to the ground. He half-expected Bishop to call the fight to an end. After all, so long as he could maintain this hold, the creature was more-or-less helpless, right?

Wrong, Raph discovered, and fast. He gaped in shock as Mack's shoulders moved under his grip. The creature seemed to melt and re-form as he held it, going from a dog-like form to a more upright stance. Now, it was taking all its own weight, and much of Raphael's, too, to its back legs, and pushing the turtles arms out and away with what felt like _hands_. As Mack turned his head, Raphael could swear that the face had changed, the previously long muzzle now shortened. The creature brought this new, shorter muzzle around to Raphael's shoulder, and bit down, causing the turtle's grip on Mack's forelegs to falter. He twisted around in the turtle's grip, standing almost nose-to-nose with him, and braced his hands – yes, they were definitely hands now – against Raphael's plastron.

Caught off-guard by these bizarre transformations, Raphael let go completely and backed away, trying to make sense of what he had just seen. Mack now looked less like a large dog, and more like a gorilla, his weight forward still but no longer moving like a four-legged animal. A word from Mikey's cheesy horror movies flashed into his head: werewolf!

But that was ridiculous. There were no such things as werewolves, everyone knew that. He tried to ignore the treacherous voice in the back of his head that said that 'everyone knew' there were no such things as mutant turtles, either. Or mutant rats, or giant alligators. Or aliens, for that matter. In his world, it probably wasn't smart put too much faith in what "everyone knew".

In his mind, he found himself frantically reviewing his knowledge of horror films. How did you kill a werewolf? He thought that maybe silver came into it somewhere, but that didn't really help him right now. Why couldn't it have been a vampire? he thought. Horror stories are full of ways to kill vampires! Why don't they tell you what to do if you're facing down a werewolf in a mad scientist's lab? He silently cursed all horror writers and their lamentable lack of foresight. And then he had to stop wondering what to do next, because Mack decided it for him.

The werewolf... creature... thing lunged at Raphael with a clumsy punch, which the turtle dodged easily, then countered with a spinning kick. It should have been a classic move, Mack's punch had brought his head in range of Raph's foot, and the kick should have landed on the side of the creature's face, forcing it to turn and face away from the next attack. Now that Mack was moving on two feet, this was more familiar ground. He'd done plenty of un-armed sparring with his brothers in the dojo; this would be no different.

Except that his brothers didn't normally use their teeth. As Raphael's foot snapped out, Mack pulled his face back to allow the kick to go past, then closed his teeth on the soft flesh of the ankle. The turtle actually cried out in pain and surprise, only just managing to keep his balance as Mack pulled at his leg. Raph seized the fur around the werewolf's ears and tried to force him to open his jaws, to no avail. The pair twisted around each other like the most peculiar entrants ever for "Come Dancing", while Bishop assiduously took notes.

Suddenly, Raphael changed tactics. Throwing himself down onto his shell, he brought his good foot up alongside his trapped one, and kicked Mack hard in the side of the head. Raph smiled with grim satisfaction when he saw that he'd placed the blow exactly right. Mack was dazed, and released his hold on Raphael's ankle.

As they both stood up again, Mack made one last lunge at Raphael. The turtle was ready for him, though. Leaning to one side, taking his weight on his good leg, he allowed the momentum of Mack's attack to once again pass by him, then he reached forward, took hold of the werewolf's arm and neatly pivoted him into the bars that stood between the fighting prisoners and their analytical jailer. Bishop didn't even blink as Mack's body came flying towards him and, as Raph expected, a jolt of electricity caught the creature a stinging blow as it came too near. Mack lay on the ground, out for the count. Raph could see blood on his temple from the kick he'd received there, and he could smell the singed fur where the electric shock had caught his shoulder.

He eyed the animal warily, but without malice. It wasn't Mack's fault they'd had to fight, any more than Leo and Mikey were to blame for their fight earlier. His thoughts went to his brothers, and he hoped they were being treated well. He glanced back to the bundle of fur at his feet, then looked at Bishop.

"We're done," he informed the scientist. "I won. Now will you let us go?"

Bishop actually laughed.

"Done? Raphael, you will find that we are very far from 'done'. I did say, this was your _first_ test, remember?"

Raphael frowned. "Yeah, OK. So, how many of these 'tests' I gotta do?"

"As many as I say, Raphael. Unless, of course, you want your brothers to take your place?"

Raphael didn't reply, and Bishop turned off the recording as Leo, Don and Mikey were looking at their hot-headed brother's scowling face.

-TMNT-

Bishop looked at the three of them, so angry and so powerless.

"The irony is, I know you're all willing to take his place at a moment's notice. It's Raphael himself who wouldn't let you do it. Quite touching, in a pathetic sort of way."

Michelangelo growled, deep in his throat, and Don threw him a worried glance. As it turned out, he should have been watching his older brother.

Whether it was the stress of the day, a residual effect of the serum, or just sheer rage at their helpless situation, something inside Leonardo snapped. Bishop's smug expression didn't flicker; as the window cover slid closed, Leo threw himself at the door, howling with rage.


	4. Chapter 4

**A/N: Thanks to StillThunder86 for being a great beta. Also, to RadicalCriminal for a very helpful review. Expect a slightly revised chapter three in a few days. Meanwhile...**

**CHAPTER FOUR  
><strong>**Progress**

Raph woke up sitting on the floor, resting against the smooth bars that had come down again between his cage and Mack's. He jerked away from them, expecting an electric shock, but felt nothing. He settled back, watching for Bishop's arrival.

After defeating Mack, he had been knocked out with another tranq dart. His arm still stung, but the implied insult stung worse. He'd promised to co-operate, in return for his brothers' safety, and Bishop _still_ didn't trust him. As far as he could tell, the only things that had happened after he was knocked out were that he and Mack and been returned to their own sides of the cell, and the double set of bars between them had been replaced. Sure, some of Bishop's men must have come in to move Mack, but what did Bishop think Raph would do to them? The turtle snorted, impatiently.

"That psycho is a total control-freak," he said. "It's like he's one a life-long power-trip."

Mack grunted, but didn't move from where he lay, curled up against the bars of his own cage. Raphael glanced at the creature, curiously.

"Mack? Bishop said you use ta be able to talk, right? Does that mean you can understand what I'm sayin'?"

Mack didn't respond, and Raphael sighed, leaning back against the bars. "It don't really matter what you do or don't understand, Mack. I gotta talk to somebody besides that scum Bishop or I'm gonna go crazy."

The werewolf, or whatever it was, made a small 'huff' sound, and flicked an ear in Raph's direction. He took it as a sign that Mack was awake, and not going to object to the sound of his voice. It was all the encouragement he needed.

"You got family, Mack? I do. Three brothers, and our father. He's away right now, visiting the Ancient One. My brothers are here, though. I hope they're OK. I saw them, on that screen over there. Leo and Mikey, with Don fussing over them like a mother hen. He does that, you know? One of us gets so much as a black eye and Donny's all over it. Wish he looked after himself half so good."

Raphael lost track of time as he talked, telling Mack about his life. He talked about small details, everyday things. About finding a beaten-up wreak of a bike and fixing it until it was the coolest ride in the whole of New York, one that even Casey Jones envied. He talked about Mikey's stomach-turning pizzas, and the time Leo spent thirty hours straight perfecting a new kata. Raphael knew he was rambling, but he didn't care. He also knew that Bishop was probably listening to all this, but he wasn't saying anything that could be used to hurt his brothers, or giving away any secrets. He took the opportunity to casually insult Bishop when recounting their past adventures. It was a small victory, but a satisfying one, to imagine the look on that superior face as he heard the turtle tell Mack about the many times Bishop had messed up.

All this talking stretched over more than just the one night. For three days, Bishop would appear in the morning with the tests he wanted from Raphael. They were ridiculously simple, either he had to fight an animal (a non-shape-shifting one this time), or complete an obstacle course. Once, he was just left sitting in a room for hours, told to wait for instructions that never came. He paced for a bit, and even practised some katas, before feeling the familiar sting in his arm and waking up in his cell. Bishop still had him tranquillised after every test, sometimes with gas, but normally with a dart. It was getting monotonous, and making it very hard to keep track of how long he'd been there. Meals were as irregular as they were boring, and Raph ate sparingly due to his suspicions about what Bishop might be putting into the food. It was no good using meals as a judge of how long he'd been locked up. But he was sure that this was the third time he'd sat and talked to Mack, which must be happening at night, he decided. When else would Bishop leave them alone for hours at a time?

He hadn't seen his brothers since that first day, but neither had he heard the echo of sirens that would mean Bishop was giving them the light and sound torture again. He stared at the blank monitor in the corner, as if he could switch it on by sheer willpower and it would give him a window into his brothers' cell. Yesterday, Bishop had told him that Mikey was fully healed, that Leo's bandages were off, and that Don was satisfied with their condition, and that this state of affairs would continue so long as Raphael "behaved himself". The turtle's temper boiled like a volcano at this, but he held it in check – barely. Bishop's 'tests', stupid as they were, weren't so bad, he reasoned, and he'd be ready for the others when they came up with a way to break out of here. After all, they were sitting around in that room all day with nothing to do but figure out an escape plan. They'd come up with something soon, he knew it.

-TMNT-

On the fourth night, or what the captive turtle assumed to be the fourth night, he woke to see Mack's cage empty. Raphael was surprised to find he was sorry about that. He'd hardly paid any attention to the creature, but it had given him someone to talk to. He knew he was probably talking to himself, but at least Mack gave the impression of listening. With the cage next to him empty, he felt foolish talking. But if he didn't talk, then how was he going to stop himself from thinking?

He got up, hoping that some push-ups or shadow-boxing would keep his mind occupied, when he heard a door open away to his right. That wasn't the door Bishop normally used, and Raphael dropped into a crouch against the back wall, using what shadow there was to try and see without being seen. As he watched, two men came in, carrying what looked like a crude stretcher between them. On the stretcher lay Mack, a deep cut slicing open the side of his body.

The men kicked open the door to Mack's cage and put the stretcher on the floor. Raph wondered why they were treating the creature in here; surely Bishop had medical rooms for this kind of thing? To his astonishment, the two men walked out of the cage, and the younger one turned to engage the electronic lock that matched the lock on Raph's own cell. They turned and headed back for the door.

"Hey, wait!" Raphael shouted, loud enough to make them turn back in surprise. "You're just gonna _leave_ him there?"

The younger of the two seemed embarrassed and looked away, but the older man just rolled his eyes.

"What's the matter, freak? You not got enough to worry about or something? You lookin' out for Mack now? Well don't bother – it can look after itself just fine."

"It's just a dumb animal, anyway," the younger one said. But the bravado in his voice rang hollow, and he couldn't meet Raphael's gaze. His eyes slid sideways to take in the still form of Mack, and he looked almost sorry for the 'dumb animal'.

His colleague caught the look, and sneered at him.

"Sheesh, kid! Not you, too? Take my advice – don't start gettin' sentimental about the freaks. It ain't smart."

"But Joe, he's…"

"'It', kid. It's not a 'he', it's an 'it'. Both of 'em, just a couple of 'it's, OK?"

The younger man nodded with a bit more confidence, and walked to the door. But he still wouldn't look at Raphael.

Raph saw red. After so many days of worry and boredom, he almost welcomed a reason to get properly angry. He couldn't give Bishop's men the pasting his fists were itching to deliver, but he could still give them a piece of his mind.

"Get back here!" he yelled. "I'll show you who's an 'it', ya filthy cowards! Couldn't get outa there fast enough, could ya? What ya scared of – Mack here gonna wake up before ya could run away? Not man enough to face us 'freaks'? Is that it?"

The door clicked closed, but Raphael didn't care. His blood was up, and he was going to keep on yelling until someone came to stop him. Maybe Bishop would turn up, if he kept going. Then that psycho "scientist" could explain what the _shell_ was happening here, and when he was going to let his brothers out.

"Fine!" he snapped. "Run away, go on! Go tell Bishop that you're scared of an unarmed turtle and a half-dead wolf. Get him in here, see if he'll face me! Hey, don't bother, I'll tell him myself. I know you're listening, Bishop! You can get your sorry ass in here and…"

"Raph." Someone said his name so quietly that Raphael almost didn't hear it. He whirled around. It wasn't Bishop voice, or his brothers', or even those two goons come back. It was a rasping voice, like someone trying to shout a whisper, and it was coming from Mack's cage.

Shocked into sudden silence, the turtle stared at the creature through the bars. The first thing he noticed was that the cut on Mack's side wasn't nearly as bad as he'd first thought. The second thing was that the animal was watching him was curiously bright and un-animal eyes.

"Raph," he said again, and this time he saw the creature's mouth move.

"Mack?" he said, taking a step forward. "Mack, did you speak?"

"Nah." It came out almost as a grunt, but the wolf-creature shook his head firmly. Casting a significant look at the monitors in the corner of the room, he said, quietly, "Can't. He say. Righ'?"

Raph frowned at looked over his shoulder to the place where Bishop normally stood. Getting as close to Mack as the double set of bars would allow, he dropped down to a crouch and spoke as softly as he could.

"Bishop doesn't know you can talk?"

Mack nodded, still keeping a wary eye on the monitors.

"So, why tell me?"

Mack paused for a moment, as if choosing his answer carefully. Finally he said, "You ge' out?"

"Get out? You mean, escape?"

Mack nodded again, more urgently this time. Raphael shook his head.

"I can't," he said. Mack huffed, eagerly.

"Can," he insisted. "I help. Can. Out."

Raph's eyes went wide in surprise. "Really?" he asked, forgetting to keep his voice down.

"Hush!" Mack barked out the order and slunk down low on the floor of his cage, keeping Raphael's body between him and the monitors.

"Yeah," he said, after a moment. "Can ge' out. Us. OK?"

Raph's face clouded over. "I can't, Mack. Sorry. I promised Bishop I'd co-operate if he left my brothers alone. I can't risk them getting hurt."

Now it was Mack's eyes that widened. "Wuh?" he said.

"Those brothers I told you about? Bishop's got them locked up here. I've seen them, and I've seen what he can do to them. Me staying here and doing his stupid tests is the only thing keeping them safe."

Mack stared at him for a moment. It was hard to read expression on his shifting face, but he seemed confused. Then understanding dawned.

"Ah, they safe, can ess… ess… ge' out, righ'? Then you?" he said. "Hmm, risk – they ge' out, forge' you?"

Now it was Raphael's turn to look confused, and only partly from Mack's odd speech patterns. He was getting the hang of working them out; it wasn't really any harder than listening to Mikey talk through a mouthful of pizza (and a lot less gross). This one, he figured, meant that Mack thought leaving his brothers in peace was some sort of master plan to allow them to plot the escape while he kept Bishop's attention. The risk, according to Mack, was that Leo, Mikey and Don would simply make their own escape, without including Raphael. It was this suggestion that made him stare.

"Of course they won't forget about me!" he said. "They're my brothers. If they make an escape plan, it will be for all of us. And yeah, sure, I'm hoping they can get me out, but when I made that promise…" Raphael paused, the image of Leo and Mikey's fight still vivid behind his eyes. He hadn't told Mack about that, and didn't want to do so now. In the end, he said, "Bishop was hurting them. This was the only way I could stop him."

"But, now he hurts _you_," Mack pointed out, still confused.

"Yeah," said Raph. "But better me than my brothers."

The huffing sound that came from the wolf-creature contained no words, but Raphael got the distinct impression that the wolf thought he was crazy.

"Honestly, Mack, I'd've busted out of here days ago if that scumbag of a scientist didn't have hostages," he said. "As it is, I've got no choice. I do what he asks, without giving him trouble, and my brothers stay safe. That's the deal."

Raph sighed and sat back. He cast a sympathetic glance at his fellow-prisoner. "Anyways, how far d'ya think you'd get with that injury?"

Mack rolled over and got to his feet. "Gone," he said, simply. Sure enough, there was no cut on his flank, just a line of dried blood on the fur.

"Woah – how'd you do that? Don' tell me ya really _are_ a werewolf!"

"Wuh? Nah, jus' fast. His thing. 'Get well soon'. Hah!"

Raph shook his head. Talking to Mack was like trying to listen to a badly-tuned radio. It made sense, in a way, but there were lots of gaps you had to fill in yourself.

"What do you mean, 'his thing'? Who's 'thing'?"

Mack nodded over to the monitors in the corner. "Him", he explained.

"Bishop? You mean, he made it so that you heal fast?"

"Yeah. An' you."

"Me? Wait, what's this got to do with me?" Raph asked, confused again.

"How's yo' ank… ank... ?" Mack began, before giving up and substituting "… foot?"

Raph looked at his foot – or rather, his ankle – where Mack had bitten him during their fight. It hadn't been hurting him at all, so he hadn't thought about it. Now that he looked, he saw that, although there was still a faint mark, the wounds had almost completely healed over. It was certainly healed far more than he would have expected in three days. He inspected his shoulder, and found no trace of the bite that Mack had given him there. The turtle raised shocked eyes to Mack, who nodded, calmly.

"Him." Mack growled, with a venomous look at the monitors. "Change you. You stay, you change. Get out," he advised.

_Could it be true?_ Raph wondered. Was Bishop really doing more 'tests' on him than the ones he'd been awake for? It made sense, the man had been so adamant about not using Don's 'tainted' DNA. But even so… well, it didn't change the fact that his brothers' lives depended on his obedience.

Wishing he could give some other answer, he turned to his new friend and said, "Mack, I told ya already, I can't!"

The yellow eyes looking at Raphael seemed suddenly colder and harder. After a long moment's scrutiny, Mack let out a huff that could have been resignation, but was more likely annoyance. Turning his back on the turtle, he very deliberately went to sleep.

-TMNT-

Another day, another round of tests, another dart in the arm. Another night, waking up in his cell. Only this time, he hesitated to talk to Mack. He knew he had nothing to say that Mack wanted to hear, but he was afraid that Bishop would notice if he suddenly stopped talking. He was still debating the best course of action, when Bishop himself entered the room.

Raph fought to banish all trace of worry or weariness from his face.

"Heh, mornin' already, eh?" he said, in passable imitation of his usual confidence. In fact, admitting to Mack that Bishop had the whip hand over him had driven it home just how hopeless his situation was. He was feeling thoroughly depressed, and in no mood to listen to the self-important, shadowy-agent's taunts today. He hoped that he could keep his temper, for his brothers' sakes.

"Not yet," Bishop replied. "It's evening, actually. I was just about to finish for the day when it occurred to me that you hadn't seen your family in a while. I'm sure you'll be wanting to thank me for my kindness." Bishop paused, expectantly.

"Yeah, sure," growled Raph. Bishop smirked, and raised his control to the monitors. Raphael fought to keep his face impassive as he watched his brothers in their own room. Mikey's bandages were off, and Leo was looking better, too. Don was standing with his back to the camera at first, but when he turned, Raph could see that he looked calmer than the last time he'd seen him. There was still no sound, but he stood and watched his brothers as they sat around talking. He wondered if they were talking about escape. Or about him. He wondered, for one bitter moment, if they missed him; but even this dark mood didn't last long. Just seeing them, knowing they were safe, lifted a huge load off of his heart.

Bishop switched off the monitor, but Raphael continued to stare at it, as if he could still see his family there. As Bishop left, he threw a curious glance at Mack, who was sitting up, ears pricked, watching the screen with as much interest as Raphael himself. When Bishop moved, Mack switched his attention to the scientist instead, growling low in the back of his throat and raising his hackles high.

Bishop allowed himself a small smile. He enjoyed being able to produce predictable responses in his subjects. However much they resisted him, he was the one in ultimate control of everything. It was a good thing to know.

"You see, Raphael?" Bishop said, his hand on the door, "You behave yourself and everyone will be just fine." He left the room, shutting the heavy door behind him.

"Liar!" hissed Mack.

Raph looked over at his fellow-prisoner, who was still glaring at the monitors. Mack always looked, and sounded, angry, but this time he seemed to mean it.

Raph found himself in the unusual position of trying to calm someone else's rage. He forced a lightness into his tone that he didn't feel. "Hey, I know Bishop's a lowlife, but what's he lying about this time?"

"See… tuh…" Mack sighed and started again. "Him… see…" he managed, before once more petering off with a frustrated growl.

Raph tried to decipher this one. It wasn't easy.

"Him?" he ventured. "Bishop, right? Something he saw?"

Mack shook his head.

"Something _you_ saw? Something about Bishop that you saw?"

Mack shook his head again, and held up a paw-like hand against further guessing. Shuffling slowly round on two feet, with one hand occasionally brushing the floor, Mack manoeuvred himself into a position where he was completely hidden from the monitors behind Raphael's shell. The turtle turned to keep him in sight but, at Mack's insistent gestures and low growls, kept his distance.

When Mack stopped moving, he closed his eyes and seemed to concentrate. His breathing became deliberate and slow, and he once more changed shape before Raph's eyes. At first he was in the half-standing crouch that he seemed to prefer when resting, the one Raphael had privately called "gorilla-Mack". As he watched his fellow-prisoner's features melt and change, Raph wondered why Mack was so keen to hide from the cameras. After all, Bishop had been there for their fight. He knew that Mack could change shape. Why the sudden need for secrecy?

But as Mack's new form emerged, Raph understood. The figure before him was still hunched over, but from choice. The way he held himself told Raph that he could stand up fully if he wanted to. The muzzle was pulled right in, leaving Mack's previously wolf-like face looking oddly flat. His front paws were now definitely hands, and the fur over all his body, while still heavy, seemed darker and smoother. Only his eyes, when he opened them again, were unchanged: yellow with flecks of brown.

Mack let out a long breath.

"Wasn't sure I could still do that," he remarked. His voice had changed, too. The whispery, hoarse quality was much less pronounced, and the diction was clearer.

"Listen, this is important. Not got long, hard to hold this shape. On screen, that your brother?"

Raph nodded, still trying to take in what he was seeing.

"Thought so," Mack said. "Saw him today, but not like that."

"What?"

"Today, I fought another turtle. Name Don Tello?"

"Donatello," Raph corrected, automatically.

"Right. Fought him today. Looked bad. Not like that," he said, nodding at the screen. "Bruises. Tired. Worried."

Raph sat back, stunned. All this, everything he'd let Bishop do to him, had been to keep his brothers safe. If Bishop was lying… He needed to know more.

"Did you see the others? Leo or Mikey? How badly was Don hurt? How much did _you_ hurt him? Where is Bishop keeping them? Did he say what he's gonna…?"

"Raph!" Mack barked. It really was a bark, too. His shape had shifted back to his resting-state, and he looked tired. "Hush," he added, looking hard at the monitors. By moving, Raphael had exposed Mack to their view, he realised. He returned to his place, and watched as Mack resumed his near-human form.

"Keep still, and quiet, and I'll tell you everything I know."

As the distraught turtle listened to the story, he wondered just what _had_ been happening to his brothers since he left them in that small, white room.


	5. Chapter 5

**A/N: Sorry about the delay in getting this posted. Thanks to everyone who's been reading, especially those who have left a review.**

**RadicalCriminal has given some very helpful feedback on the fight scenes, and StillThunder86 continues to be a fantastic beta.**

* * *

><p><strong>CHAPTER FIVE<br>****Progress?**

Donatello shifted anxiously from foot to foot as he waited for the door to be opened. He heard the bolts drawn back, then the crack of the hinges as the grey steel finally swung aside and let him see his brother. Leonardo was sitting up, which was better than last time, but his left arm was a mess of bruises. Don sighed.

"What happened this time?" he asked, resignation in his voice. This wasn't the first time he'd been called on to tend his brothers, and he doubted it would be the last. At least Leo didn't need stitches.

"That's not your concern, freak," said one of the guards. "Just check him over and see if there's any bones broken. And no funny stuff – remember?"

Don didn't need to be told twice. Crossing the room swiftly, he began checking Leo's bruises.

"What happened, Leo?" he asked, softly. "How did you get these bruises?"

His older brother looked at him curiously, his eye-ridges pinched together in confusion.

"I… I'm not sure," he said. "I think, something was coming towards us, too fast. No, I was too slow. Too slow!" Suddenly Leo was angry, grabbing Don by the shoulders and almost shaking him. "I wasn't fast enough, Don! Mikey… he…"

"It's OK, Leo, I'm seeing Mikey next. I'm sure he's fine. It's not your fault," Don could've wept to see his confident oldest brother so beaten. He mumbled soothingly, not paying attention to what he said, desperate to see the pain go from Leo's eyes.

Leo himself felt as though he was living in a nightmare. His family was divided, and he had been powerless to protect them since the ambush. How long ago was that? A week? A month? A year? He had lost all sense of time, living in this small room and only allowed out to take part in Bishop's games. He hadn't seen Raphael since they were captured. He remembered his brother fighting furiously, going up against six armed men. Bishop's hired muscle, Leo thought. Skilled, efficient. Deadly. Leo's heart seemed to stop beating. He had seen Don, and Mikey, but not Raphael. There was only one explanation for this, wasn't there? And that's why he was here, being punished. He was suffering because he hadn't saved his brother. Because Raphael was dead.

He was aware of Don's voice, but didn't take in any words. He thought that he was talking, too, because Don suddenly grabbed hold of both his shoulders and shook him, albeit gently.

"No, Leo, Raph isn't dead," Don insisted. "You saw him, remember? We all did – fighting that weird creature. He won that fight, remember? He's here, and he's alive."

Leo raised his head and looked at his younger brother. "Alive?" he repeated, sounding half-asleep. "Raph's alive? And Mikey?"

"Yes, Leo."

The eldest turtle blinked, as if trying to make sense of this information. Finally he said,

"Don?"

"Still here, Leo."

"Am _I_ alive?"

The guard stepped up, pushing Don away from his patient.

"Very touching. I may puke," he snapped. "How's the arm? Anything busted?"

Don shook his head. "No bones broken, and no muscles torn as far as I can tell, just over-strained. He just needs to rest that arm until the bruises fade, then some gentle exercise until he's fully recovered." He was under no illusions that his advice would be followed, but he felt better for saying it. And at least Leo would know how to look after himself the best he could until Don's next visit.

He was forcibly escorted from the room, leaving Leo sitting there, looking like he'd lost all hope. Don dropped his gaze, his throat tight with emotion. He made himself breathe slowly, and regained his outward composure a little.

"OK," he told the guards. "I'll see to Michelangelo now."

"Say 'please'," prompted one of them, and the other laughed, nastily.

"You'll see who we say, when we say. And don't forget it!"

Donatello didn't rise to the bait, but even he was finding it difficult to keep his temper recently. He wondered how Raphael was coping. Or maybe he wasn't? Maybe he'd done something to upset Bishop, and Leo and Mikey were being punished for it? Don tried squash the thought that Raph was somehow to blame for what was happening to them all. This was all Bishop's fault, he reminded himself. Whatever his hot-headed brother had done, or not done, this whole, horrible situation was down to Bishop, no-one else. But if what was happening to Leo and Mikey was a reaction to something that Raphael had done, what would come next? Would Raph go the whole way and try to break them out, or would he back down to save them? Should Don be preparing himself and his brothers for an escape attempt?

He was still caught up in this flow of unanswerable questions when the guards either side of him stopped. They had been walking down a corridor of nondescript grey to another door, identical to the one that had shut behind him when he left Leo. No time to wonder about what Raphael might or might not be doing – he was here for Mikey.

-TMNT-

Don's breath caught in his throat as the door opened to reveal his youngest brother. Mikey was lying on his bed, seemingly out cold, and his whole left side was bloody mess. His shell had a few cracks running up the side, and his leg was covered in cuts. His arm looked broken, and he had a black eye blooming over an open gash on his cheek. Don stood and stared, until one of the guards pushed him to step forwards.

"Get on with it," he ordered. "We ain't got all day, ya know."

Don walked quickly to his youngest brother's side and began to clean and dress his wounds. Mikey was awake, and Don saw that his face was tight with pain. In an effort to keep his distracted, Don asked,

"What happened, Mikey?"

Michelangelo breathed steadily, forcing himself to focus on Donnie's voice rather than the pain in his side. He thought out had been worse earlier, but maybe that was just his imagination. Taking a deep, steadying breath, he tried to remember exactly what had happened in that room. He knew that Leo was there, and it was hard because he kept thinking of that nightmare fight under the influence of Bishop's foul serum.

"Mikey?" Don's concerned voice cut though his dark thoughts. "Do you not remember?"

"Yeah, Donnie, I remember." He sighed, then hissed a Don started to clean the largest cut on his leg. He hoped talking would take his mind off the pain.

"It was an obstacle course, like the one we did yesterday. Only, this time it was harder, faster. And it was worse for Leo, I think. He was moving kinda stiff, like he was still feeling the bruises from... from..." His face clouded at the memory of exactly how Leo had got those bruises. Don paused in his bandaging and patted his youngest brother's knee gently.

"It's OK, Mikey, don't think about that anymore. It's over," Don promised.

Mikey blinked back tears, nodded once and continued with his story.

"Yeah, well it was a room, like I said, with all these obstacles in - you know, walls to get over, pits to jump, balance beams - the works. The one yesterday was kinda lame, Leo even said Bishop was insulting us with such basic exercises. Maybe he shouldn'ta said that, cos the one today was _not_ easy. Everything was bigger, and the stuff that moved was faster. Then there was the last bit - not funny even for Bishop. This one was like a wall, moving up on us and we had to get across in front of out. There wasn't enough time, and the exit was only big enough for one at a time, and I could see it in Leo's face that he was going to make me go first, so I just grabbed him and pushed him through the door before he could start arguing. I was halfway through when the wall hit, and it... well, you can see," he said, glancing down at his injured side.

Don grimaced and finished bandaging the cleaned injuries, glad that none of them needed stitches. He wanted to tell his brother that everything was going to be OK. Trouble was, he didn't believe it himself.

-TMNT-

Back in his own cell, Don allowed himself to shudder. He had held his emotions in check while he'd been attending to his brothers, partly as a matter of pride that he shouldn't let Bishop's henchmen see how upset he was, but mostly to keep Leo and Mikey from worrying about him – or each other. So long as he got to see them both he could tell them that things were OK, under control. Even though they weren't. It was three days since they'd taken Leo and Mikey to separate cells, and five since they'd seen Raph.

He wished Agent Bishop would let him visit Raph. He'd asked often enough. He'd even tried to insist, but that had come to nothing. The scientist had told him that, though Donatello's knowledge of their mutated chelonian physiology was useful, he was by no means irreplaceable. If he wanted to keep the 'privilege' of being his brothers' doctor, he would do as he was told.

He let himself flop down onto the shelf that served him as a seat and a bed, letting out a frustrated sigh. He didn't dare push the matter of seeing Raphael, not when Mikey and Leo needed him. Leo, especially. His physical injuries were superficial, but Don was getting very concerned about his eldest brother's state of mind. Mikey was holding up well, by comparison, though his physical injuries tended to be worse than Leo's. The effects of the Bishop's serum appeared to have completely worn off in both of them, but the frustration and humiliation of being held captive were taking their toll. On all of us, Don admitted to himself.

He was glad, in a way, that he didn't have time to brood on their situation. Bishop had said he had other tests which didn't involve DNA, and Don had quickly found out what that meant. For the past two days, he had been set to fight a variety of opponents. He had faced trained bodyguards on the first day, skilled in unarmed combat. These matches had been hard, and Donatello was forced to call upon all his knowledge of ninjitsu to avoid serious injury. Still, they had been supervised tests, with Bishop taking careful notes throughout. It was better than a street fight, if only because he knew he was facing professionals. He could attack with precision, being fairly confident about the way his opponent would respond. The day had been gruelling, but bearable. Today had been much worse.

The first fight was against a woman, smaller than him but an effective fighter. He had tested her strength at first, then settled into a routine combat. He hadn't enjoyed it; he never really enjoyed fighting, not the way Raph or Leo, or even Mikey did, but he'd got through the match without too much difficulty.

The second was against a young man – a boy really. From the first, Don could tell that he wasn't a fighter. It showed in everything about him, from the way he stood, to the terror in his eyes. Turning away from the boy, he addressed Bishop directly.

"What's the idea, Bishop? What's he doing here?"

"You don't want to fight him?" queried the scientist.

"You know I don't."

"Not even when I tell you that he's one of the guards seeing to Raphael? He's been very rude about your brother, you know. Calling him a freak, referring to him as 'it'. Don't you want to teach him a little respect?" Bishop's tone was even; he might have been delivering a weather report for all the emotion in his voice. But there was an expectant look in his eyes that shone with malice.

Don gave the quivering boy a hard look. The kid paled.

"That wasn't me!" he wailed, desperately. "It was Joe. Joe said all that stuff about the… your brother. Not me! I didn't mean… please don't hurt me!"

The turtle rolled his eyes. "Honestly, Bishop, let the kid out of here before he wets himself. I'm not going to fight this one. This is ridiculous!"

"You are going to fight, both of you," Bishop corrected. "Because I tell you to, and you know the penalty for disobedience. Greaves, you have a choice: you can fight Donatello here, or you can fight Mack." The boy, Greaves, turned horrified eyes to his boss.

"No," he breathed. "You wouldn't… not after…"

"I see you remember," Bishop remarked. To Donatello, he added, "Mack really doesn't like humans, for some reason. Doesn't like anyone, of course, but get particularly vicious around humans. There was one case, Simon… well, we needn't go into that. Right, Greaves?"

Greaves shook his head, the horror in his eyes making then seem too big for his skinny face.

Bishop nodded, once, apparently satisfied. Turning to the turtle again, he said "Donatello, you also have a choice. You can fight of your own free will, or I can try the latest strain of the serum on you. It will be interesting to see how much you remember of the encounter afterwards. Of course, the whole thing is being recorded, so you'll be able to refresh your memory anytime. I wonder what it will be like, watching yourself kill a defenceless boy? And, of course, there's the matter of your brothers." Bishop's neutral expression hardened. "If you are still standing there doing nothing in ten seconds, I shall consider it an act of defiance. And you know what that means."

Now it was Don's turn to pale, though it hardly showed under his green skin. He stood, undecided. How would Leo handle this? he thought. I can't just attack this boy. Then he had an idea. He walked over to the trembling Greaves and stood squarely before him.

"Hit me," he said.

"What?"

"Three seconds," Bishop observed.

"_Hit me_!" Don commanded, and Greaves obeyed almost on instinct. Don caught the clumsy blow and twisted the boy away, using his arm as a pivot. He held the arm firmly, pushed Greaves towards the back wall and appeared to be wrestling him into an arm lock.

"You've seen my brother? How is he?" Don whispered, as the boy struggled to get away.

Greaves' eyes, which had been screwed shut with the effort of pushing back at the turtle, suddenly opened in shock. "He's… he's OK," he replied.

"Really?" Don asked, then added, "Keep struggling, we've got to make this look good."

Greaves nodded, squirming in Don's grip and managing to twist out of his hold. The turtle 'slammed' the boy against the wall, as gently as he could.

"Really! I saw him yesterday, he's good," the boy insisted. "What do we do now?"

"Take my arm – the way I was holding yours. Good. Now, push against me, hard as you can," Don instructed. If he thought of it as a dojo lesson, maybe he could get through this. He had to imagine he was teaching a student. A particularly inept one, he thought, with a trace of bitter humour.

He was contemplating the least painful way to bring the fight to an end, when Agent Bishop's voice cut in again.

"I don't believe either of you are really trying. Do you need further incentive? Very well, the loser of this fight will go on to face Mack. How's that?"

Greaves looked sick with terror. He took another clumsy swing at Don, which the turtle easily dodged, allowing the boy's arm to pass his shoulder. Facing away from Bishop, and acting quickly, Don grabbed Greaves' other hand and placed it against his own throat.

"Hold there," he whispered. Greaves stared, but didn't move his hand away. Unfortunately, he didn't move at all. Don leaned forward, trying to show the boy what was excepted of him, but apparently the threat of "Mack" had frozen the boy completely. Bishop began to make impatient noises from behind the glass, and Don had to think fast.

He took hold of Greaves' arm and flipped him round so that the boy's back was against Don's plastron.

The turtle sighed. This wasn't going to be easy.

"Listen," he whispered, patiently. "Drive your left elbow into my bicep. My upper arm," he added, when Greaves hesitated. "Ow! The other left, kid," Don hissed.

"Oh, yeah. Sorry." Greaves tried again.

"Good. Now that you've made me let go of you, swing round with your right arm… right arm… and grab my neck. Yeah, like that." The hold was pathetic, but Don did his best to stay within it.

"Now, left hand, in a fist, to the side of my head. Well done," Don whispered, as he let his body go limp and slide to the floor. Greaves didn't let go fast enough, and was taken down with him, landing in a tangle to sprawled limbs.

"Hey, er, turtle, you OK?" he whispered. "I didn't kill ya, did I? Did I?"

Don opened one eye to give the boy an exasperated look, then closed it again to once more play dead.

Bishop looked up from his clipboard.

"Well, you certainly showed him," he said. The tone was level, but Don could hear the sarcasm in it. Greaves, it seemed, could not.

"Thank you, Mr Bishop, sir," Greaves said, getting up and beaming as if he really had defeated the ninja turtle single-handed.

"Greaves, get out," Bishop replied, not looking at him. "Stone, send in Mack."

The boy scurried from the room at top speed, just as a panel opened in the far wall.

"I suggest you 'wake up', Donatello," Bishop sneered. "Time for a real fight."

-TMNT-

Don got to his feet as Mack padded into the room. He did a double-take at the sight of the animal – surely this was the same creature they'd seen fight Raphael? For a split second he thought he saw something like surprise in Mack's eyes. Before he could think too hard about this, however, Bishop's voice came through the speakers set into his observation window.

"Donatello, I believe you've seen Mack in action before. There will be no play-acting here. You are facing a killer: expect no mercy."

There was a click as Bishop shut off his microphone, and then the only sound in the room was the padding feet and steady breathing of the two combatants as they circled one another, watching for an opening.

Don watched the animal closely, while careful to avoid direct eye contact. He wanted to gauge when Mack was going to spring, but not provoke an attack. He wondered what would happen if he made himself entirely non-threatening. Bishop claimed that Mack was a killer, but animals didn't tend to attack without a reason. Perhaps if he waited, Mack would lose interest. Bishop couldn't blame Don for that, surely? The turtle risked a glance towards the man behind the glass. Oh, yeah. This was Agent Bishop. He wasn't known for his reasonable nature. He could probably find a way to blame anyone for anything, if he wanted to.

Don turned his attention back to Mack. The pacing had slowed until they were almost at a standstill, on opposite sides of the room. The turtle risked a quick look at Mack's face, trying to judge the animal's mood. What he saw made him stare.

There was a calculating look in the animal's eyes that was quite unnerving. Don wondered how much Mack understood about their current situation. Did he know Bishop was watching them? Could he grasp the concept of a set-up fight? Had he seen Don's fight with the boy Greaves, and did he realise that Don wasn't the instigator of this fight? The turtle examined Mack's features closely. Bishop had called the animal a killer, and Don could believe it. Strangely, though, Mack didn't have the air of being a vicious animal. He seemed almost to be studying Don; perhaps he was interested and intrigued by the turtle?

Or perhaps he was looking for a place to attack, Don thought, as Mack came sailing towards him, claws out and jaws open. The turtle managed to dodge at the last moment, rolling to one side. He felt the fur on Mack's side brush past him as he moved out of the way, and silently thanked Master Splinter for the hours of training that kept his reflexes sharp.

Mack's momentum carried him past the turtle and almost into the far wall. He changed shape in mid-air, bracing newly-formed hands against the wall as it approached, and landing on two feet. He spun to face the turtle, and immediately lashed out another attack with his unsheathed claws.

Don turned away from Mack's blow, and heard the sound of claws skittering over shell. He reached back and caught hold of Mack's wrist, keeping the claws pointing away from his skin. He pulled the animal towards him, scissoring his legs around Mack's neck and using his right arm to make a triangle, trapping his head. Mack tried to turn and bite the turtle's stomach, but was foiled by the ridges of Don's plastron.

Mack was already doubled over, and swiftly transitioned back to a four-legged form. Don watched in amazement as the head before him changed. The ragged, triangular ears became rounder and smaller, the muzzle shrank back into the head and the shaggy brindled fur became smooth and black. When Mack had entered the room, he had looked most like a wolf. Now, he more closely resembled a panther.

Don felt himself lifted up on powerful shoulders, and fought to keep his balance. Mack lifted him clear of the ground, then shrugged him off. The turtle landed on his back, rolled quickly and got to his feet in one, fluid movement. He faced Mack again, ready for the animal's next attack, but found himself distracted by curiosity about this strange creature's abilities. He knew how to fight humans, and had faced various mutants of one kind or another. He knew that the principles of ninjitsu would work against animals, too, but he was unsure about how to face an opponent who was neither one thing nor the other. He'd never been taught how to fight a shape-shifter, and was not certain what his next move should be. Don felt an inner surge of frustration, and resentment at their situation. He didn't _want_ to fight Mack, he wanted to study him! This creature represented a whole new field of research, not to mention his apparent intellige...

He'd done it again, Don realised, as his legs shot from under him. He'd stood there, lost in thought, while a dangerous opponent charged at him. He sighed and tried to get up, but Mack was pinning him down. The big cat was lying on top of him, breathing down his neck. He looked up into the creature's face and felt a moment of fear. It would only take one bite from those powerful jaws and Don would never draw another breath. But as he lay there, trying to keep still and calm his heart rate, he saw a look of satisfaction cross the feline features. It wasn't the look of a killer who'd taken down his next meal; it was more the expression of someone who had… well, yes, just won a difficult fight. A look he himself had worn after a successful session in the dojo with his brothers.

The dart hit Mack with such force that it rocked Don on his shell as he lay trapped underneath the creature. The pleased expression faded to blankness as the animal passed out, and the turtle slid himself out from under the dead weight. Bishop ordered Donatello back to his cell and watched thoughtfully as his men to removed Mack from the room.

Donatello left the room in a daze, with more questions than answers about the mysterious 'Mack'. Not only was the creature not the vicious killer Bishop claimed, but he was almost certainly sapient. As the turtle headed back to his own cell, he wondered if Raph had noticed the same thing during his fight with Mack. He wondered where his brother was right now and, Greaves' reassurances notwithstanding, if he was alright.

-TMNT-

"You wanted to see me, sir?" A very nervous Greaves stood in Bishop's private office. He'd never been in here before, and by all accounts this was where the boss worked on his most secret projects. He fixed his eyes on the carpet. People only got called in here to be praised, promoted, or… let go. He thought he could guess what fate awaited him.

"Do you think I'm stupid, Greaves? Do you think you are cleverer than I am?" Bishop asked, his voice cold and quiet.

Greaves continued to stare at the carpet. "N-n-n-no, sir," he stammered, shaking his head violently.

Bishop sat in silence, looking hard at his young henchman. He knew that Greaves' imagination was torturing him with fears about how he would be punished, and this suited Bishop nicely. He allowed a full minute to pass before he spoke again.

"I don't like it when people try to deceive me, Greaves," he said. The boy went pale and started to tremble.

"You will take a pay cut, backdated to the beginning of the month. You and Harris will be on night security until further notice." The boy's head came up at that.

"Joe Harris?" he repeated. "Why's he on nights? What'd he do?"

Bishop looked down at his paperwork, as if no longer interested in the boy before him.

"He works with you. I won't have the efficient running of this base disrupted by re-arranging the work teams. You are both transferred, and you can explain it to Harris." Greaves pulled a face. He could just imagine what Joe would have to say when he found out about this.

"Your first shift starts in two hours," Bishop informed the stunned Greaves. "Dismissed."


	6. Chapter 6

**A/N: Thanks to everyone who's been reading this - especially to my reviewers.**

**As always, big thanks to StillThunder86 for being a great beta and picking up on things I didn't explain clearly.**

* * *

><p><strong>CHAPTER SIX<br>****Action**

"Mack? Have you got it yet?"

Mack glared at Raphael but didn't reply. He was up against the door of his cell, reaching through the bars to tap the keys of the electronic lock. It was difficult, having to work by feel and input the combinations on a reversed pad, but he knew he could do it – if only a certain turtle would let him concentrate.

"Only, it won't be long before ol' B. spots what we're up to, and then…"

"Yeah, yeah," Mack grunted, feeling for the final button. The lock beeped, and he almost fell out of his cell. He immediately started work on Raphael's lock. This one was much easier, as he could stand facing the keypad and see what he was doing. Within seconds, the door clicked open and Raph stepped out. He cast a wary eye at the monitors.

"How long until someone notices us?" he asked.

Mack shrugged, as if being caught was an unimportant detail. He headed towards the door to the right of the cages. The two of them moved silently; Raphael walking with a ninja's light tread, and Mack on four feline paws. They went through the technician's door and Mack raised his head and sniffed. The wolf-like snout quivered as he detected the scent the fresh air, and he trotted determinedly down the corridor.

Raph followed her."Wha'dya got, Mack?" he asked. "Is Don this way?"

Mack stopped and turned his head to look at the turtle. "Nah. Out." he said, adding, "Air," by way of explanation.

Now Raphael stopped, planting his feet firmly.

"We're not leaving without the others," he insisted. "Where are they?"

Mack rolled his eyes, but didn't argue. He sat and listened carefully, then started nosing the floor. He walked in a slow circle, then set off at a brisk pace back the way they had come.

They moved quickly and quietly through the empty corridors. Raph was surprised (and a little disappointed) not to meet any security guards as they went. They must have been picked up on camera several times by now, but so far no-one had come to stop them. Every time the pair had reached a junction, Mack had paused to pick up their new direction while Raph looked about keenly for any sign of guards.

Now Mack stopped, outside a grey metal door with a large '3' painted on it in white. Through the small window Raph could see…

"Don!" he said, delightedly. "Hey, Don, we've come to get you out, bro!"

Donatello was crouched in front of the monitor in his cell, tinkering with what looked like a set of wires. He didn't turn around.

Raphael blinked. Why was his brother ignoring him? The turtle turned to Mack.

"Can ya get this door open?" he asked. The shape-shifter gave a non-committal noise, stood up to reach the key pad, and entered a few different combinations. The light on the lock stayed stubbornly red.

"Move over, let me have a go." Pushing Mack aside, Raphael punched a few random buttons. Frustrated by this lack of success – and Don's still not looking round – the turtle slammed his fist into the lock. It gave a loud bang and spat sparks for a few seconds, causing Raph and Mack to jump back. When they looked again, Donatello was standing in the open doorway.

His relief at seeing Raphael quickly changed to concern when he spotted Mack.

"Hey, Don – we're busting outa this joint," Raph said. "Oh, this is Mack. He's on our side. Where's Mikey and Leo?"

He addressed the question to Mack, but it was Don who answered.

"This way," he said. "And hurry. I don't know what you did to my door, but I'll bet it set off some kind of alarm."

Raph frowned as he hurried to keep up with Don's fast pace. "'Thanks for gettin' me out, Raph', 'Hey, no prob, Don'" he said, sarcastically. "What I 'did to your door' was get it open – while you just sat there ignorin' me. And, I don't hear no alarm." His voice softened slightly when he saw the Don really did look worried. "Relax," he told his brother. "We ain't seen a single guard all evenin'."

-TMNT-

"Shut off that racket!"

Greaves fussed with the panel under the flashing light until the alarm stopped.

"Sorry, Joe," he said. They were the only ones in the guards lounge, and Joe had the TV on to catch a late movie. Greaves picked up his torch and nervously gestured towards the door.

"Um, shouldn't we go and, sorta, see what set the alarm off?" he ventured.

"Do what you want, kid," said Joe, without taking his eyes off the screen. "Just don't bug me any more tonight, OK?"

"Um, yeah. OK. I really am sorry about this, Joe. I…" Greaves faltered under Joe's disapproving silence, and finished, "I... I'll go and make sure everything's OK."

Joe sighed as the door closed behind his junior colleague. He ought to ease up on the kid, he thought. After all, at least he didn't get Greaves' pay-cut, so night-shift meant better wages. And it was easy work, to be honest. With everything locked down tight, and surveillance covering every inch, security guards had nothing to do but go on the occasional patrol. And he got to carry a gun. It was a pretty cushy number, really. Maybe, when Greaves messed up enough to get himself sacked for good, Joe would get to stay on night-duty for this sector. No more carting around great heavy test subjects? Better pay, nice uniform and a proper gun? Yeah, thought Joe, I could get used to this.

-TMNT-

"You just _had_ to say it, didn't you Raph?" said Don.

The three escaping prisoners had rounded a corner to see a uniformed figure coming towards them, torch in hand. Mack's hackles rose. He shifted to his most wolf-like form and tensed for attack, but Don laid a hand on his head to stop him. The wolf's ears went flat and he flinched at the touch. Raph's eyes widened in shock, sure his brother was about to lose a hand, but Don didn't seem to notice any of this. Instead, he went forward himself, silently keeping to the shadows until he was close enough to speak to the guard.

"Hi," Don said, keeping his voice low. "Greaves, right?"

The guard dropped his torch, and nearly screamed in shock. Don caught the torch before it hit the ground and held a finger to his lips urgently.

"Shhh! Greaves, it's me."

Raphael and Mack peered around the corner and saw Don having an urgent, whispered conversation with the young security guard. Mack stiffened, but Raph motioned him to keep still.

"Don knows what he's doing," he assured his friend. "Let him handle this."

After a minute or so, Don waved for them to join him. The guard flinched when he saw Mack.

"Hey, you never said you had Mack with you!" he protested. He backed away until both turtles were between him and the wolf-like Mack. "You're crazy, bringing that animal with you. You'd better keep it away from me, that's all."

Mack's ears flattened against his skull and a low growl started in the back of his throat. Raphael now recognised the guard, and understood Mack's reaction. He almost wanted to growl himself. Then a thought struck him.

"Hey, I saw you here in the day yesterday," Raph said. "How come you're on nights, too?"

Greaves went red. "The boss is mad at me," he confessed. "When he finds out I let you guys go, I don't know what he'll do." Then he seemed to cheer up a little. "Hey, at least he can't make me fight Mack, right? Not if you all get out tonight."

Don took Greaves firmly by the arm, before he could say anything more to offend their fellow-escapee.

"Where's that store-room, kid?" he prompted. Turning to the others, Don added, "Greaves here knows where Bishop put our weapons. He's going to show us the way, right?"

Greaves nodded and set off down a side corridor, careful to keep a safe distance away from the still-angry Mack. After a minute, he stopped outside a plain wooden door.

"In there," he said. "It's the key with the long handle," he told Don.

Don sorted through the keys and card-keys that he'd taken from Greaves, selected the right one to unlock the storeroom, then pushed the young guard ahead of him through the open door. While Raph and Mack collected the belts, masks and weapons, Don picked up a piece of discarded cable and loosely bound Greaves' hands behind his back.

"We'll lock you in, kid," he said. "If anyone asks, we overpowered you, stole your keys and forced you to tell us about the storeroom. OK? That ought to keep you out of trouble with Bishop. Though, if you've got any sense you'll find another job as fast as you can."

Raph and Mack left the room, carrying the turtle's possessions. Greaves relaxed slightly now that he was no longer in the same room as the werewolf, but he still looked pale and scared. Don turned to him for one last question.

"How many guards on duty tonight?" he asked.

"Um, just me an' Joe in this bit," said Greaves. "An' Joe's not gonna come out patrolling 'less he has to. He's mad at me for getting him put on nights."

Don nodded, once, and patted the uniformed shoulder. "Thanks, Greaves," he said, before bringing his hand up sharply against the side of the boy's head. As the guard slumped to the ground, Don set him carefully against the wall and left the room, locking the door behind himself. Raph and Mack were waiting for him outside.

Raph turned to Mack.

"OK, we need to find Mikey and Leo now," he said. "Can you track them?"

Mack shook his head.

"Can't you even _try_?" Raph almost shouted.

"No scent," said Mack, flatly.

"I know where they are," Don cut in, quickly. "I was taken to see them both when... woah – Mack can talk?"

Mack glowered at him, but said nothing. After a long moment of silence, Raph answered for him.

"Yeah, Mack talks. When he feels like it," he added, bitterly.

Don lead the way to Michelangelo's cell, with Raph and a still-silent Mack trailing behind. Soon they came to another grey door, labelled with the number '7' in white paint. Raph looked through the window while Don searched for the key-card that matched the lock on Mikey's door.

"Hey, Mikey!" Raph called, "It's us! We're gettin' you out!" The youngest turtle sat on his bunk, staring blankly at the opposite wall, and ignoring Raphael completely. A pile of discarded dressing lay in a heap in one corner of the room, but, Don was astonished to note, there was no trace of the serious injuries he'd treated only hours before.

"Hey, shell-for-brains, over here!" Raph said, louder this time. He reached past Don to knock on the glass just as Don swiped the lock. The door clicked open and Mikey's head snapped round at the sound.

"Oh, _now_ he stops ignorin' us!" Raph muttered. Don gave him a strange look.

"The door is probably sound-proofed, Raph. I know mine was," he said. Raph's face turned as red as his newly-recovered mask, and he didn't say anything as he handed Michelangelo his own mask, belt and weapons. _So that was it_, he thought. _And me thinkin' Bishop had made Donnie deaf or somethin'_.

"Thanks, guys," Mikey said. He sounded tired, and carried his left arm a little stiffly. He looked around to see a tall, shaggy figure standing behind his brothers and carrying Leo's equipment. He leapt immediately to the wrong (if understandable) conclusion, and stared at Mack in horror.

"Leo?" he whispered. "Is that you?"

Don, Mack and Raph looked at Michelangelo as if he'd gone mad.

"We haven't got Leo out yet," Don said, carefully. "This is Mack. He's helping us."

Raph looked like he wanted to say something at that, but Don didn't give him time. "Come on, this way," he said, and took off at a swift pace down the seemingly endless grey corridors.

Don was leading the way, with Mikey close at his heals. He seemed to be waking up with each step, although he still held his left arm a little stiffly. He'd tucked his chucks into his belt, and made no move to wield them – unlike Raph who, now that he was no longer carrying Mikey's gear, had his sais held firmly in his grip, ready for the first sign of trouble.

As they rounded a corner, they came face-to-face with a man wearing a white lab coat and carrying a clipboard. He stared at the four of them for only a second before his hand went for his pocket. Quick as a flash, Mikey grabbed the man's wrist.

"Hands where we can see ' em, mister," he drawled, in his best John Wayne impression. Turning to the others, he added, "I always wanted to say that."

The man's other hand was reaching for his pocket, but Mikey put a stop to that by delivering a neat chop to the back of the neck. The technician passed out with Mikey still holding onto his wrist, so that for a moment the turtle looked like a referee in a boxing match.

"Ladies and gentlemen, the winner is - me!" he announced.

Raphael cuffed his brother on the head. Mack stiffened. They didn't have time for a fight here! Even a short scuffle might attract more attention than they could deal with. He stepped forward, ready to stand between the combatants. To his surprise, there was nothing to stop. Michelangelo wasn't poised to answer his brother's challenge, nor was he backing away. He was laughing, which Mack couldn't understand at all. Turtles, he thought, must be different from wolves, or even cats. It was a puzzle alright, but one for another day. Right now, they had to focus on escaping.

Meanwhile, Don has been going through the pocket that the technician had been reaching for. He lifted out a PDA.

"Brilliant," he said, smiling broadly. "I got a bit of information from hacking the monitor in my room, but this will be much better." He promptly began pressing buttons, frowning with concentration and ignoring the others. After only a few seconds, he smiled and slipped the PDA into his belt.

"What'cha got there, Donny?" Michelangelo asked. Don smiled to hear some of Mikey's enthusiasm returning, even though the hardship of the last few days still showed in the dark circles under his eyes.

"I managed to pull up a rough map, and got an idea of where this base is. We're not that far from where we left the Battle Shell, if we can just get out of here."

Raphael glanced over his shoulder. Don and Mikey were following him closely, but Mack lagged behind. Raph saw him turn to look down a side corridor, and he seemed about to go down it alone when he checked himself and followed after the turtles. Raph felt his anger fade. He was still annoyed that Mack had refused to help find Leo and Mikey, but he knew that the werewolf was risking a lot by getting them all involved in this escape. He let Don pass him as he waited for Mack to catch up.

Mikey stopped too, and Mack watched them both warily as he got nearer.

"What?" he said, drawing level.

"You OK?" Raph asked. "What's that you were looking at?"

"Air." Mack said. "Out," he added.

"That's the way out? Down there? Great!" Raph said. "Soon as we get Leo, we'll head straight for the door."

Mack frowned, as if he wanted to ask why they didn't go _now_, rather than wasting time on Leo. Still, he knew better than to annoy Raphael by saying that out loud. Instead, he gave his usual non-committal grunt and walked on beside Raph.

By the time they got to Leo's cell Don already had the door open. Leo came out looking dazed, and even more tired than Mikey had. He didn't seem to be injured, but he walked like he was asleep. Quickly, Raph took Leo's katana from Mack and passed them to his eldest brother.

"Come on, Fearless, snap out of it!" he ordered. Leo's hands closed around the hilts of his swords and he seemed to come alive. Mack could tell at once that this was the leader of the four brothers. Even Raphael seemed to defer to Leo, although he probably didn't realise he was doing it. Leonardo moved with confidence, despite the bruises which mottled his left arm, and which must have been causing him some pain. He slung the sheathed weapons into their place on his back, then put on his mask and belt. His eyes seemed brighter as he took in the sight of his brothers, safe and whole. He paused as his gaze fell on Mack, who was already poised to head back the way they had come, towards the exit.

"That's Mack," said Mikey, noticing Leo's expression. "He's okay. Come on, we're getting out of here!"

Leo cast a look around the corridor.

"Wait," he said. "There's a camera that way. We need to stay out of the line of sight. If anyone saw you coming this way, they'll think you carried on in the same direction. Stealth, everyone – now!"

Mack watched, amazed, as all four turtles seemed to vanish into the shadows. He himself shifted to his most panther-like form, as having the darkest fur, but even with his enhanced night vision he could hardly see where Raphael and his brothers had gone. The hall seemed full of half-light, and they were just four shadows among shadows.

"Hey, Mack? Come here, where the camera can't see you." It was Michelangelo's voice, and Mack turned towards it. Now that he had a direction, he could just make out the edge of a shell. He padded forwards until he was standing next to Mikey. His tail lashed a little at being given orders, but he kept still and quiet.

As they all stood, frozen, waiting for the camera to sweep past them, Mack took stock of the two brothers he had met before. Mikey seemed relaxed – almost too much so, given their situation – and it was a new sensation for Mack to be so close to someone who didn't fear him. However, he filed this in his mind under "investigate later", because Leo was there too, and the signals he was getting from this turtle were all too familiar. From the tense way he was standing, the set of his jaw and the short, controlled breaths that Mack could just about hear, it was obvious that Leo didn't feel happy about the shape-shifter's presence. Leo didn't seem afraid, exactly, but a sense distrust and discomfort was coming off him in waves, and making Mack himself feel nervous.

He was also a little uneasy at being so close to these strangers – and armed strangers at that – but neither of them attempted to lay hold of him. Mack released the breath he'd been holding, and prepared to follow the turtles' lead. With the four of them working together, he realised, they stood a much better chance of making this escape successfully. For the first time, Mack thought that Raphael had been smart to include all his brothers in the break-out.


	7. Chapter 7

**A/N: This chapter marks the end of part one. Part two is still being written and beta'd, but it will be with you ASAP.**

**I hope you're enjoying the story so far. Thanks to everyone who's reviewed and/or favourited. And, as always, big thanks to StillThunder86 for being a great beta.**

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><p><strong>CHAPTER SEVEN<strong>  
><strong>Choices<strong>

Back in the guards' lounge, Joe was jerked from sleep by the persistant beeping of an alarm.

"I told you to shut off that racket, Greaves!" he growled, without opening his eyes.

The alarm continued to blare at him, and Joe finally got up and stumbled over to the control panel himself.

"Greaves? Where are you, ya useless lump?" he called. There was no answer. Then he remembered, the kid had gone to out on patrol. Joe glanced at the clock on the wall. What was taking him so long, he wondered. And why had the alarm stared up again, after Greaves switched it off? Joe cast a look around the cosy lounge, and patted his new holster. If he wanted to keep this job, he'd better go and make sure that everything really was alright, right? Not that anything could get loose around here, not with all the surveillance and security and all, but still, it wouldn't hurt to show a bit of initiative, would it?

Idly he wondered where his junior partner had gotten to, then dismissed the thought. He was glad Greaves wasn't with him – the kid would only end up doing something stupid that would make them both look bad. Joe checked the location of the alarm on the computerised map of the building and saw that a technician had triggered his personal alarm somewhere between holding cells seven and nine. That was close enough to the main entrance to be a cause for concern. Joe wondered if Greaves had accidentally set it while on his own patrol - messing with a PDA that didn't belong to him, or something equally stupid. He smiled at the prospect of getting the idiot fired for good. Joe set off, swinging his night stick and swaggering a little as befitted his smart new uniform.

-TMNT-

The five escaping prisoners made it back to the corner that Mack said lead to the exit. Leo and Don were at the front of the group with Mack walking between them, scenting the way to the exit. Mikey came next, and finally Raph, keeping a watchful eye out for trouble from behind. After a few more turns, Mack stopped beside a box set into the wall, about four feet off the ground. It was an opaque grey and held closed with a padlock.

Mack moved a little distance away from the turtles, and slowly rose into his most human form. He steeled himself mentally. This was the crunch – if the escape failed now, all would be lost. He was trusting these strangers with everything. Part of his mind screamed at him not to be such an idiot, but he ignored it.

"These are the locks, operating the main gate," he said, indicating the box on the wall, and pointing to another exactly like it on the other side of the corridor. Mack made an effort to speak clearly, shaping his face as close to human as he could, though his panther fur still covered his body, and his long tail twitched with the effort of staying balanced on two feet.

"Which of you is the fastest runner?" Mack asked.

Mikey instantly said, "I am!" Raph rolled his eyes but didn't contradict him. Leo and Don nodded.

"Yes, Mikey's the fastest of all of us," Don confirmed. "Why is that important?"

"These locks are meant to be opened by guards," Mack explained. "Once the code is entered, the gates remain open for only a few seconds. Both codes must be entered at the same time. I take one, and... Mikey... does the other. The res' of you, at gate. It open – we run, 'kay?"

Mack's voice had grown more guttural during this speech, which was the second longest he had made since he couldn't remember when. Don watched with mounting interest as Mack's muzzle visibly lengthened, but Raph nodded to show that they'd understood. Moving in his stooped, bipedal form, Mack shuffled over to the box and broke the lock with one swipe of his clawed hand. He indicated the keypad inside.

"3, 7, 2, 5, 1. 'kay?" Mack pointed to each button in turn, careful to avoid pressing any of them. Mikey watched closely.

"3-7-2-5-1, gotcha," the turtle repeated. Mack grunted once and went over to his own box. He saw that Raph was already there, having broken the padlock with one of his sais.

"Ya OK to do this one, Mack? You don't move so fast on two feet," Raph said, quietly.

"Yeah, fine," Mack assured him. "Go four feet to run, go fas'."

"Everyone ready?" That was Leo's voice, calling from beside the gates where he stood with Don. "Raph, get over here!"

As Raphael turned to join his brothers, they were all dazzled by a beam of torchlight. A uniformed guard stood in the mouth of the corridor, blocking off their retreat.

-TMNT-

Joe stared at the sight before him in horror. He hadn't expected to find any real trouble here, and certainly not to see Mack walking about loose. He froze, barely registering the other shadowy figures before him. He saw Mack's body flow from upright to four-legged as the creature lunged straight for his throat. He had no time to aim as he pulled out his new gun and squeezed the trigger, praying that he hadn't left the safety catch on.

-TMNT-

The impact of the shot killed the momentum of Mack's leap, stopping him dead in the air when he was just inches away from the guard. The shot had gone wide, but only just. Instead of hitting the shape-shifter in the chest, the bullet had merely torn through the outer muscles of the shoulder. As Mack fell to the ground, he was aware of the turtles rushing past him to overpower the guard and take away his gun. Within seconds, Joe was lying on the ground several feet away and out cold. Raph stood over him, sais at the ready, but didn't deliver the final blow. Mack blinking slowly, unsure of what he was seeing. As Raph and Leo walked away from the fallen guard, the shape-shifter let his eyes close. His shoulder was on fire, and he was in no mood to puzzle out his friend's peculiarities.

Don knelt at Mack's side, turning him over to get a look at his wounded shoulder. He stared in amazement as it began to close up of its own accord. Mack opened his eyes and flinched away from Don's touch with a growl.

"It's OK, it's only me," Don said, quickly lifting his hands from Mack's side. "Can you get up? We need to move before anyone else gets here. That gunshot must have attracted some attention."

Mack raised himself onto three legs, and managed to limp to the box. He shifted to a more upright form, but it was a slow process. A look of panic crossed his face. He knew he'd be OK to run again within half-an-hour, but they didn't have half-an-hour. They barely had half a minute to spare. Raph was at his side in a flash.

"It's OK, Mack. We can still get out – just tell me the code for the lock."

The look of panic didn't fade, if anything it intensified. Mack shook his head, eyes wide.

"No," he rasped. "I can't stay here – can't!"

Donatello shot a puzzled look at his brother, but Raphael only said, "Go wait by the door, Don." As the purple-masked turtle left, Raph stood in front of Mack and looked him straight in the eye.

"You won't stay here, Mack. Go and stand by the door, and be ready to run – but tell me the code, first."

The panic left Mack's face, to be replaced with confusion. He stared in silence, before managing to say, "...why?"

The turtle laid a hand on Mack's good shoulder. "You're a friend. We don't leave people behind."

Mack seemed to wilt under the weight of Raph's touch. Looking at the ground, he said, "4, 7, 3, 9, 2."

Raph nodded, then pushed Mack gently towards the door, where Don and Leo were waiting.

"Everybody ready?" Mack smiled to himself. That was Leo. Even without Raph's stories, Mack could have guessed that Leo was the alpha of this pack. He couldn't seem to stop himself from taking charge of everything.

"Ready!" called Mikey.

"Yeah, go for it," Raph said. There was silence as the two brothers entered the door codes, then the main gates hissed as they moved apart.

"Run!" yelled Leo, as Don helped Mack through the opening. Mikey sprinted forwards and made it through easily, but Raphael, only a few paces behind, almost got the ends of his bandana caught in the closing gates. Leo grabbed his brother' arm and pulled him clear just in time.

As the five prisoners moved away from the underground complex towards their van, they were watched by Bishop on a monitor in his office. The agent's face was unreadable, but he made no move to summon guards. He watched them until they were out of range, then turned his attention from the CCTV to a small computer screen where a tracking light began to move steadily towards New York.

He allowed himself a barely perceptible smile.

-TMNT-

They had emerged from a tunnel mouth, and found themselves in arid surroundings. Donatello glanced at the PDA he'd borrowed, confirmed their direction, then threw the device back down the tunnel.

"They can probably track these things," he explained. "No sense making life too easy for Bishop and his goons."

Mack walked in his resting form, shuffling on two feet and occasionally touching the hand of his uninjured arm to the ground for balance. He and Raph were walking together, a little apart from the others. The pair were silent for a long time, and seemed to be thinking hard. The shape-shifter's shoulder was healing fast, and he was carrying his arm much more naturally when Raph finally spoke.

"Mack," he said, carefully, as if uncertain how to ask the question, "Why did you think we would leave you, back there? I mean, you saw how I got my brothers out, right? You know I wasn't going to leave them behind – why would we leave you?"

Mack blinked, surprised. "They're usefu'," he managed, at last.

Raph frowned. "Useful?" he repeated, disbelief in his voice. "What's that s'posed ta mean?"

Mack sighed. He would've preferred to have this conversation in more human form, but he was exhausted from his rapid healing. He knew that if he tried to change shape now, he wouldn't have the strength to keep walking. So, after some thought, he said, "Usefu'. Don, knows com... com... knows stuff, Mikey's fast, an' Leo knows s'ra'gey. St'a'gy. S'ra... how to no' get caught," Mack puffed out a breath after this list. He hoped Raph got the picture, because he didn't think he was up to any more explaining.

Raphael felt his jaw drop. After everything he'd told Mack about his family, did the creature really think that he'd only saved his brothers because they were _useful_? He didn't even know how to _begin_ explaining things to someone so, so… he didn't even know how to describe it! Where did you start, against an attitude like that? Fortunately, at that moment, Don wandered over from where he'd been talking to Mikey, and interrupted them.

"Mack, were you ever human?" he asked.

The sudden change of subject caught Mack by surprise. "Wuh?" he said.

Don didn't seem to register Mack's reaction. "Only, I've noticed you have trouble talking when you're in your more animal shapes, right?" he said, the light of scientific investigation in his eyes. "I think it's because you're trying to speak like a human, but your animal forms don't have the right type of face muscles. Did you always know how to talk, or did Agent Bishop teach you?"

Mack growled at the mention of Bishop's name. "I know. He no' teach. Hah!"

Raph opened his mouth to interpret, but Don seemed to have understood.

"I thought so," he said. "It shouldn't be too hard for you to learn how to use your animal muscles to speak. You should ask our father, Master Splinter, for some advice. He's a mutant rat, and he doesn't have any trouble talking – in English or Japanese. He's away visiting right now, but he'll be back in a month or so." Don looked at his brothers. "Mack can stay with us for a bit, right?"

Leo hesitated. He was always cautious about bringing strangers to their home, and would have preferred to know more about this "Mack" before letting him near the Lair. Mikey, however, was delighted at the prospect of a new friend.

"Sure! Our casa is your casa, right, dude?" he said, flinging an arm casually around Mack's shoulders.

The effect was electric. Mack sprang forward as if he'd been stung, spun round and dropped into a defensive crouch, eyes wide and flickering between all four brothers. There was a tense, awkward moment.

It was broken by Raphael slapping his youngest brother upside the head.

"Knock it off, Mikey!" he snapped. "When you gonna learn, not everyone's as into hugs as you are?"

Mack cocked his head, curious, but his hackles settled back down and he straightened up as much as his current form allowed. He seemed embarrassed, but managed to look the question at Leonardo, as leader of this pack: _May I_?

Leo seemed to consider for a moment, then nodded.

"If you wish to stay with us, you are most welcome," he said. His tone was perhaps a little stiff, but the invitation was genuine. Mack nodded, and followed the turtles away from the only home he'd ever known.

He didn't look back.

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><p><strong><em>Continued in Part Two<em>: Unnatural**


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